In the meantime, if you (or someone you know) are experiencing difficulties with the online installer, try the Qt SDK Repo Chooser. It sets up a repository locally that points to a mirror of your choice, which would hopefully give you a better download experience.

So far, I've provided a Windows build. I have successfully run the Windows build on Ubuntu 14.04 through Wine in Windows XP mode, although the repository path needs to be converted from a Windows path to a Linux path.

If you'd like to contribute another build (especially an OS X one), I'd be happy to host it on the GitHub downloads page.